Add Userflow (Staging only)

[kaapstorm]

Technical Summary

Important

This is only open for review

The Product team will be evaluating Userflow on Staging for guiding users and improving feature awareness.

Jira: SAAS-19721

This change is paired with PR dimagi/commcare-cloud#6870

Safety Assurance

Safety story

Only affects Staging.

Automated test coverage

No

QA Plan

No

Rollback instructions

• This PR can be reverted after deploy with no further considerations

Labels & Review

• Risk label is set correctly
• The set of people pinged as reviewers is appropriate for the level of risk of the change

[millerdev]

Is setting a global required (and the best way) now that we're on Webpack? Wonder if @nospame or @jingcheng16 might have input on that?

[kaapstorm]

Yes, I would be interested in a better way to do this. The objective here is for userflow to be available in base.html so that is can be initialized and associated with request.couch_user.user_id.

[kaapstorm]

How about ce5432f ?

[millerdev]

Since this is only for staging, maybe put the branch on staging (before merging) to verify that it works (both with and without a real USERFLOW_TOKEN in settings)? I couldn't tell from the PR description if this has already been tested in both of those modes, but the "without" mode seems especially important since it will be the one that applies on non-staging environments.